The rotating chef hats are for venting hot attic air not appliances. You really need to consult your HVAC guy. A lot depends on the location the vent will penetrate and even more on the type of roof you have.

Well, we are DIY but I will go to the HVAC supply store and ask my local experts there... DH is a systems tech (plumbing, electrical, HVAC, mechanical) but in the marine industry. He's perfectly competent to install and service stuff, but things like this we need advice on!

I would doubt that ice dams of any significance would occur for any roof steeper than 4:12, and plausibly for even lower pitches. Not only is the heated area small, but the heat (BTUs per hour times hours of use) exhausted due to cooking is much less than the household heat passing into an attic in cases where ice dams are a problem. I had a major ice dam this winter at the edge of the roof over my kitchen, but the kitchen ceiling was insulated by only a tarp.

However, the question of blockage is an interesting one.

A sufficiently wet and heavy (yet blowing) snow might pile up in a way that reduces the aperture of the style roof cap that Broan, say, uses for the larger model fans. However, these fans have overhang at the exit (down side) and I doubt that total blockage would occur. So long as some air can pass, then pushing out warm air should clear a larger hole as needed. I won't be able to attest to that until next winter, but I can say that here in southern NH, when in use a Nutone mushroom style exhaust fan with an air exit point about 10-inches above a 5:12 roof, has never been blocked by snow in 20-some years.

If a snowstorm were found to be depositing snow that was suspected of being perverse in the blockage sense, then running the fan during the storm should maintain sufficient air clearance to allow the fan to work when the snow hardens up.

kas

The engineers that design remote blowers and caps for venting co.'s are way smarter than your local appliance salesman.

Don't you think that they considered their firm might sell a cap/blower to someone that lived in an area that had heavy snow? Think they figured that they should design their system and install instructions to deal with that?

Still think your appliance guy has a clue?

Thanks folks--- Yeah, I was doubtful of his advice and that's why I wanted to run it by this forum!!! He had that air oftrying too hard to be the expert.... but you never know, and I am certainly not an expert! Thanks for the feedback!

just a thought...is there any way you might be able to vent out the side of your house instead of the roof? I'm probably only about an hour south of you, and when our vents (hood, bath, dryer, etc.) were being installed, the HVAC guys did everything possible to NOT punch them through the roof...specifically because of the potential for ice damming...